In 1892 I communicated to this Society an account of a collection of Eurypterids from the Upper Silurian rocks of the Pentland Hills, in which I described new species and a new genus. Since that time I have had the opportunity of examining two other collections from the same locality. One of these was formed with the aid of a grant from the British Association. The fossiliferous bed—for these remains occur in a single thin bed of rock—was laid bare, and a considerable amount of it removed and split up. In this latter work I was fortunate to get the assistance of Mr John Henderson, the original discoverer of the locality, and I am glad to have this opportunity of recording my indebtedness to him. A fair number of specimens was thus procured, which not only threw considerable light on the structure of some of the already described forms, but gave evidence of some species as yet undescribed. More important than this collection, however, was the one formed by the late Mr Hardie of Bavelaw Castle, who had for many years collected among the Pentland Silurians. His collection was, on his death, acquired by the Edinburgh Museum of Science and Art, and Dr Traquair kindly put the collection in my hands for examination. From the size of the collection I expected some new and interesting results, and have been far from being disappointed. Seven new species of Eurypterids have come to light and one Scorpion.